First, this is on a server, so I have no logs.
Whenever this particular diamond shulker box is loaded, I crash with the following message.
Internal Exception: java.lang.IllegalArgumentException: Payload may not be larger than 32767 bytes

I putting this here in case it's an iron chests thing. If not, I was using Mekanism boxes to load chests into this chulker box for transport.

I just faced this issue yesterday, when i filled up an Iron Shulker Box, the player is kicked with a similar error message as above. The player will not be able to log-in until the Shulker Box is removed.

We just managed to do this and can test if we can reproduce it. It happened when adding the MoreChickens mod eggs to it. They have a lot of NBT data and then the moment you look at it you crash. We had it removed by using the /fill command to fill the space with air.

I believe we can reproduce this in dev, will update if we can.

If I remember correctly, I was placing both forestry bees and gendustry genetic templates in the shulker box when this happened. Note that when getting too close to the box the bug also crashes the game.

You might want to check out https://github.com/CoFH/Feedback/issues/865. Similar problem and they fixed it.